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Old 06-06-2012, 06:56 AM   #10
rwidman
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City: North Charleston, SC
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Quote:
Originally Posted by ben2go View Post
A battery isolator.I prefer marine spec,even on RVs, as they don't have as much issues with humidity as automotive grade.Maybe it's just me being paranoid,but I think they are sealed better and use better quality internals.

Just to add.Size them a little larger than your alternator's max output.Say your alt puts out 100 amps use a 130A or even better a 150A.
A battery isolator is "old technology". It works using large diodes to keep the batteries seperate. The problem is the .7 volt (more or less) voltage drop through the diodes doesn't allow the batteries to charge fully.

Much better is a "battery combiner", also known as a "voltage sensing relay" or "VSR". A VSR senses the charging output of the alternator and when present, connects the batteries together through a relay. When there is no charging output, the relay drops out and disconnects the batteries (or banks) from each other.

This is one example: Combiner 160 Sheet

edit: I see Jeff pretty much already said what I said. It works. That's what I used on my previous boat and it's what is on HIGH COTTON although it's a brand I've never heard of.
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